The present invention relates to power transmission units for motor vehicles.
Transmission units are known of the type which comprises a transmission casing shaped to conform with a change-speed gearing contained therein, the change-speed gearing including an output mainshaft rotatably supported from an upright end wall of the casing, and an extension housing secured in a fluid-tight manner at its upright front seating face to the upright end wall to contain one end of the mainshaft extending therein from the upright end wall, the extension housing forming therein a lubricant chamber in open communication with the interior of the casing through the upper portion of the upright end wall.
In operation of the transmission units as described above, lubricating oil in the transmission casing is picked up by rotation of the change-speed gearing and flows into the lubricant chamber through the upper portion of the upright end wall. Thus, the lubricating oil is stored in the lubricant chamber to lubricate component parts assembled within the extension housing. Although the transmission casing is provided with a drain plug to drain off waste lubricating oil and with a filler plug to feed in fresh oil, the waste lubricating oil in the extension housing may not be drained off due to closed state of the upright end wall, and the fresh oil may also not be supplied into the lubricant chamber at the initial stage of operation.